Heating system

ABSTRACT

Shrink wrap apparatus includes a heating chamber, an air heater mounted alongside thereof and a forced air recirculation system for blowing hot air into the bottom of said chamber and extracting cool air from the top.

United States Patent 1191 Kostur July 30, 1974 HEATING SYSTEM 3,404,50810/1968 Dreyfus 53/30 1 1 199999911 199991919 Koswr, 11 Brighten L9,22128523 351323 fifiiiif jiji:3333:3111:1131;133:3313 32/53? Oak BIOOk,lll. 60521 3 522 3/1970 3,526,752 9/1970 [22] Filed. July 27, 19723,605,283 9/1971 [21] Appl. No.: 275,558 3,717,939 2/1973 PrimaryExaminer-John J. Camby [52] US. Cl 34/225, 34/233, 354513864, AssistantExaminer ]ameS Yeung [5]] 1m Cl F26) 25/06 Attorney, Agent, orFirm-Fidler, Patnaude & Batz [58] Field of Search 34/66, 216,- 219, 224,225,

34/230-234, 236; 53/30, 184 AFSTRACT Shrmk wrap apparatus includes aheating chamber, an 56] References Cited air-heater mounted alongsidethereof and a forced air UNITED STATES PATENTS recirculation system forblowing hot air into the bot- 3 070 897 1/1963 Lowe 34/225 tom of saidchamber and extracting cool air from the 3:222:800 12/1965 Siege] 5511i3.309.835 3/1967 Peppler 53/184 1 Claim, 5 Drawing Figures I 47 5 A 5144i 1 45 i 44 43 i 44 J i 36- a; 1 45 4a 45= --36 U I ill 1|| 1 In J aHEATING SYSTEM The present invention relates in general to a system forrecirculating air between an air heater and a heating area, and itrelates more particularly to an apparatus and method for wrappingarticles such as pallets with a heat shrinkable plastic film.

BACKGROUND OF THE INVENTION The use of heat shrinkable plastic film forpackaging various types of articles is well known, and such film hasalso been used to enclose and secure separate articles or other materialon pallets in manufacturing and warehouse facilities. The equipment thusfar available for heating and shrink wrapping such large size packageshas not been particularly satisfactory.

OBJECTS OF THE INVENTION Therefore, an object of the present inventionis to provide a new and improved method and apparatus for applying heatto a plastic material.

Another object of this invention is to provide a new and improvedheating tunnel adapted for handling large items to be shrink wrapped.

A further object of this invention is to provide a new and improvedshrink wrap system adaptable for use with pallets.

SUMMARY OF THE INVENTION Briefly, the above and further objects may berealized in accordance with the present invention by providing a heatingtunnel through which articles loosely covered with an inverted bagformed of heat shrinkable plastic film are carried by an intermittentlydriven conveyor belt, and an air heater and blower mounted adjacent tothe tunnel and for circulating hot air frombottom to top in the tunneland for recirculating the air from the tunnel through the heater. Doorsare provided at both the entrance to and the exit from the tunnel, andthese doors are automatically operated in synchronism with the conveyorbelt to minimize the loss of heat to the surrounding area.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages and abetter understanding of the invention may be had from the followingdetailed description taken in connection with the accompanying drawings,wherein:

FIG. 1 is a perspective view of a shrink wrap machine embodying thepresent invention;

FIG. 2 is a vertical section of the machine of FIG. 1 taken along theline 22 thereof;

FIG. 3 is a plan view of the machine of FIG. 1, the ends of the conveyorbeing omitted; and

FIG. 4 is a vertical section of the machine taken along the line 4-4 ofFIG. 3;

FIG. 5 is a horizontal sectional view of the air inlet control of FIGS.3 and 4.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings andparticularly to FIG. 1 thereof, a shrink wrap machine includes as itsprincipal parts a heating tunnel l0 enclosing a heating chamber, an airheater and recirculating unit 11, and a conveyor belt 12 for carryingthe articles to which heat is applied within the heating chamber. Asillustrated in FIG. 1 the conveyor 12 incorporates a plurality of spacedapart transverse members 13 and travels from left to right through anentrance (not visible) at the left into the tunnel l0 and out of thetunnel through the exit at the right. Pairs of motor operated doors 14are provided for the entrance and exit openings and are opened andclosed in unison by electric motors 15 which are energized insynchronism with one or more electric motors 16 which drive the conveyor12.

As shown in FIG. 1, the machine is being used to wrap pallets 17 of thetype commonly used in factories and warehouses and transported by forklift trucks. The loaded pallet at the left is loosely covered by a heatshrinkable plastic bag 18 with the sides of the bag overhanging the deckof the pallet. While in the tunnel hot air is blown onto the bag whichcauses it to shrink and thus tightly engage the pallet and its load toprovide a tightly wrapped unit as shown at the right in FIG. 1.

Referring more particularly to FIGS. 2, 3 and 4, the heater sectionincludes a burner 20 which directs a flame into a heat exchange orfiring tube 21 across the hot surface of which return air from theheating chamber is drawn by a blower 22 driven by an electric motor 23.The thus heated air is forced by the blower 22 into a duct 24 lyingbeneath the floor 25 of the tunnel 10. The duct 24 underlies the entirefloor 25 which is heated by the hot air and radiates heat upwardly intothe heating chamber. Three inlet ducts 26, 27 and 28 are spaciallypositioned in the front sidewall 29 of the tunnel and three similarducts 30, 31 and 32 are positioned in the rear sidewall 33 directlyopposite the ducts 26, 27 and 28. All of these vertically disposed inletducts open at the bottom onto the bottom duct 24 and are closed atthe'top, and are each provided with a pair of upper rectangular openings35 and a pair of lower rectangular openings 36 from which the hot airenters the heating chamber. Respectively mounted within the wallsbetween the vertical inlet ducts are a plurality of outlet ducts 37 and38 at the front end 39 and 40 at the rear. The outlet ducts are providedwith upper and lower rectangular inlet openings covered by screens 41for preventing foreign materials from entering the air circulating andheating system.

In order to enable high speed operation of the machine it is importantthat the hot air be directed against the plastic film and that a minimumof hot air escape from the tunnel while the doors 14 are open. To thisend a horizontally slidable baffle 43 is provided for each opening 35and 36 and each baffle has a flange 44 extending into the chamber.Similar flanges 45 are fixedly positioned along the opposite edges ofthe air inlet openings whereby air entering the heating chamber travelsin a direction perpendicular to the front and rear sidewalls 29 and 33.Where desired, the movable baffles may be positioned to completely closeoff the associated openings. Where, for example,only one pallet is beingwrapped at a time as shown in FIG. 2, the baffles 43 covering theopenings in the inlet ducts 26, 28, 30 and 32 may be closed. The flanges44 and 45 also prevent the hot air from short circuiting the chamber andpassing directly from the outlet openings into the inlet openings.

The air outlet ducts 37 and 38 are closed at the bottom and open at thetop into a return air duct 47 which extends across the top of the tunnell0 and connects to a return air duct 48 which opens at the bottom intothe chamber housing the firing tube 21. In order to provide equaldistribution of hot air to both sides of the heating chamber, anadjustable butterfly valve 50 is mounted across the inlet side of theduct 24 downstream of the ducts 26, 27 and 28.

lt is important that the lower edges of the bag 18 surrounding theopening therein be heated more quickly than the upper portions so thatthe mouth of the bag shrinks onto the pallet before the top shrinks andpulls the mouth portion away from the pallet. For many applications theflow of hot air from bottom to top through the tunnel together with theradiation from the floor provides the desired heat differential. Wherenecessary, however, auxiliary hot air inlets 51 are provided in thefloor 25 beneath the conveyor 12 for blowing hot air directly onto thebottom of the pallet through the openings in the conveyor between themembers 13. These auxiliary inlets are provided by tubes cut on a biasat the bottom and rotatably mounted in the floor 25 between theillustrated position wherein air is directed upwardly through the openconveyor belt, and adjacent thereto and the opposite position wherein noair is blown therethrough toward the conveyor belt.

OPERATION In operation, the doors 14 are closed and the burner 20 andblower 22 are energized until the air being circulated through thetunnel reaches a temperature of about 350F. Loaded pallets may then beplaced on the loading side of the conveyor belt, heat shrinkable bagsare then loosely draped thereover and the drive system is actuated toopen the doors l4 and drive the conveyor to carry the pallets into thetunnel. The conveyor then stops and the doors close for about sevenseconds during which time hot air is directed against the bags on theone or more pallets positioned in the tunnel. Under the control of atimer the doors then open and the conveyor carries the completed palletsout of the tunnel and simultaneously carries one or more additionalloosely wrapped pallets therein. This machine is readily adaptable tofully automatic or semi-automatic operation and features thereof may beused for purposes other than shrink wrapping.

While the present invention has been described in connection with aparticular embodiment thereof, it

will be understood that those skilled in the art may make many changesand modifications without departing from the true spirit and scopethereof. Accordingly, the appended claims are intended to cover all suchchanges and modifications as fall within the true spirit and scope ofthe present invention.

What is claimed is:

1. Apparatus for wrapping pallets with heat shrinkable plastic film,comprising a heating chamber having a floor, mutually parallel sidewalls, and an imperforate ceiling,

duct means positioned directly beneath said floor in heat conductiverelationship therewith,

means for passing heated air through said duct means to heat said floor,

first and second sets of ducts extending in a vertical direction inopposite ones of said side walls,

said first set of ducts being connected at the respective bottoms tosaid duct means,

a controllable damper mounted in duct means for controlling thedistribution of heated air to the ducts in said first set,

duct means disposed above said ceiling and connected to the tops of saidsecond set of ducts,

said first set of ducts being separated from one another by said secondset of ducts,

a plurality of openings in each of said first and second sets of ductscommunicating said ducts to said chamber,

a plurality of vertically disposed elongated baffles respectivelydisposed on said side walls between adjacent ones of said openings todirect air entering said chamber in a direction perpendicular to saidside walls,

a perforate conveyor disposed on said floor for supporting a pallet inclose proximity to said floor, and

a plurality of spaced apart conduit means mounted in the upper wall ofsaid first mentioned duct means directly beneath said conveyor forcontrollably di recting separate streams of air upwardly toward thepallet.

1. Apparatus for wrapping pallets with heat shrinkable plastic film,comprising a heating chamber having a floor, mutually parallel sidewalls, and an imperforate ceiling, duct means positioned directlybeneath said floor in heat conductive relationship therewith, means forpassing heated air through said duct means to heat said floor, first andsecond sets of ducts extending in a vertical direction in opposite onesof said side walls, said first set of ducts being connected at therespective bottoms to said duct means, a controllable damper mounted induct means for controlling the distribution of heated air to the ductsin said first set, duct means disposed above said ceiling and connectedto the tops of said second set of ducts, said first set of ducts beingseparated from one another by said second set of ducts, a plurality ofopenings in each of said first and second sets of ducts communicatingsaid ducts to said chamber, a plurality of vertically disposed elongatedbaffles respectively disposed on said side walls between adjacent onesof said openings to direct air entering said chamber in a directionperpendicular to said side walls, a perforate conveyor disposed on saidfloor for supporting a pallet in close proximity to said floor, and aplurality of spaced apart conduit means mounted in the upper wall ofsaid first mentioned duct means directly beneath said conveyor forcontrollably directing separate streams of air upwardly toward thepallet.